As a display device for displaying an image, development of an organic electroluminescence display device using an organic electroluminescence element as a display element has been advanced. Furthermore, the organic electroluminescence display device is used for not only a direct view type display but also a microdisplay for requiring a pixel pitch of several microns. In the following description, there is a case where the organic electroluminescence element is abbreviated as an “organic EL element” and the organic electroluminescence display device is abbreviated as an “organic EL display device”.
In the direct-viewing type organic EL display device, normally, a red light emitting unit, a green light emitting unit, a blue light emitting unit, and the like are selectively coated by a mask vapor deposition process or the like. However, it is difficult to selectively apply the coating in the organic EL display device used for the microdisplay since mask positioning accuracy and the like is required. Therefore, the red, green and blue light emitting layers are laminated over the entire display region to obtain white color, and colorization is performed by using a color filter.
Furthermore, in an organic EL display device having a so-called top emission structure, it is necessary for an upper electrode to be configured to transmit light. Therefore, it is necessary to form the upper electrode by using a transparent conductive material such as ITO or IZO. However, since a sheet resistance of the transparent electrode becomes relatively higher than that of an electrode made of a metal material such as aluminum, a problem such as reduction in image quality caused by a voltage drop or the like may occur. If the film thickness of the transparent electrode is increased, the sheet resistance can be lowered. However, a problem such as reduction in transmittance occurs.
Therefore, to substantially lower the sheet resistance of the transparent electrode, an auxiliary wiring is provided separately from the transparent electrode. For example, Patent Document 1 discloses that an auxiliary wiring is provided on a substrate side opposed to a substrate on which a transparent electrode is provided, and the auxiliary wiring and the transparent electrode are connected by a contact. Furthermore, Patent Document 2 discloses that an auxiliary wiring is formed to be superposed on a transparent electrode.